Background: Little is known about the intention formation process regarding the use of tracheostomy and invasive ventilation (TIV) in amyotrophic lateral sclerosis (ALS) patients in the course of disease progression. Objective: To clarify the intention formation process in the use of TIV in ALS patients for the purpose of providing decision-making support. Methods: We conducted a follow-up study of 14 patients using semi-structured interviews, participant observation, and medical records review. Results: The patients' various intentions regarding the use of TIV were formed as their symptoms progressed (e.g., declining motor, swallowing, and respiratory functions). Other factors influencing their decision were their considerations, such as their ability to communicate after receiving TIV treatment, the degree of support they would receive from professionals after TIV treatment, palliative care for physical distress, value of life after TIV treatment, and to what degree they would be a burden on their families. Conclusion: Patients' intentions regarding the use of TIV were diverse and changeable. The decision of whether or not to use TIV was made out of conviction as well as considering individual experiences of symptom progression and quality of life after TIV use.